A common practice in the packaging of IC's (integrated circuits) is to mount the IC die (chip) onto a header which electrically connects the pads of the chip to complete the electrical connection to the socket pins. This assembly is then encapsulated in a plastic potting compound such as epoxy. In some cases, epoxies are used to adhere the lid to the base of an IC body. However, moderately high temperatures may cause this epoxy to release gaseous products which may damage the IC. Moisture coupled with internal IC materials has been a cause of catastrophic failure in some IC and hybrid systems. In the industry, an epoxy seal is generally considered not to be hermetic, since epoxies may gradually leak gaseous products from the surrounding atmosphere into the IC.
An alternative to plastic packaging is hermetic packaging. Some IC's and hybrid systems do not permit plastic encapsulation because of the application environment; for example, military standards for hermetic packages typically dictate that the seal material be metal. One type of hermetic seal in the prior art comprises an alumina ceramic base with printed wiring connections to electrically connect the package pins to the pad connections of the IC chip. The chip is surrounded by a suitable metal ring body, such as "Kovar," which is hermetically sealed to the ceramic base. A lid is then hermetically sealed to this metal body. The hermetic sealing operation requires high temperatures to seal the lid to the body while at the same time providing an internal inert gaseous atmosphere. Another type of package is ceramic with plated metal seal (e.g. W, Ni and Au) surfaces on the upper edge of the base and on the lower edge of the lid. Solders (e.g. SnPb, SnAu) are typically used to solder seal the lid to the base.